MISSION BAY (CBS 8) - Dozens of volunteers with the San Diego Audubon Society on Sunday were in Mission bay to prepare for least tern breeding season.
The endangered birds return to the San Diego region to breed mid-April, and conservationists cleaned out invasive plants while they set up protective structures.
"This is not a naturally occurring sand dune. Fiesta Island was created artificially and so we get lots of weeds out here and the birds need to nest on totally open sand dune," said Megan Flaherty, Conservation Project coordinator.
While least terns are considered an endangered, their population has rebounded since the 1970s.
The group of volunteers placed weeds in thick trash bags to ensure a safe space where the seabirds can raise their young.
"This is our last big event out here. We are two weeks away from the birds arriving and we have over 60 volunteers out here removing invasive weeds from this nesting site," said Flaherty.
Since January, the San Diego Audubon Society has been out every weekend - totaling about 2,000 hours of service to prepare for the least terns return.